Rush Street Gaming, the company aiming to develop a slots parlor in Millbury, was on the hot seat recently for allowing a compulsive gambler to remain in its Philadelphia casino for three days straight in February.

It was the third time this gambler, who had put himself on the state's casino exclusion list because of problem gambling, was caught in the casino. He had been previously discovered after four nonstop days of gambling in July 2012 and an earlier incident in January 2012.

"We take the self-exclusion list very seriously and do our best to ensure that people who put themselves on it do not enter our casino. As we have done in every place we do business, we will partner with the state and local authorities to make sure that people who put themselves on the self-exclusion list stay out of our Millbury casino," said Justine Griffin, a spokeswoman for Rush Street Gaming.

The February incident at SugarHouse Casino, operated by Rush Street Gaming affiliate HSP Gaming L.P., was not included in the Massachusetts Gaming Commission's investigative report of Mass Gaming & Entertainment LLC. The report, dated May 31, was the basis for the commission's approval July 11 of Mass Gaming & Entertainment's suitability to apply for a slots casino license.

While noting a $10,000 penalty and consent agreement between the Pennsylvania Gaming Control Board and SugarHouse Casino, issued in December 2012 after the second incident of the self-excluded person gambling for days, the Massachusetts investigators wrote: "The investigation also revealed that after corrective actions were implemented, violations were reduced and compliance strengthened. The occurrence of these violations do not reveal any inherent or systemic weakness nor any pattern of intentional or negligent disregard of regulatory compliance responsibilities and none were deemed material to adversely impact the suitability of either the qualifying entities or individuals."

However, on July 11 Commissioner James McHugh said about several Rush Street Gaming facility exclusion violations, "I must say I was troubled by the number of incidents and the fact that they didn't seem to disappear, notwithstanding the substantial fines that were imposed and the training regimens that were instituted."

Elaine Driscoll, a spokeswoman for the state Gaming Commission, wrote in an email Monday: "The Investigations and Enforcement Bureau is aware of this incident. As with every applicant, the Investigations and Enforcement Bureau maintains open lines of communications with gaming control boards in other jurisdictions. Ultimately every applicant will be judged by the totality of their compliance record. In addition, any applicant who is awarded a license by the Massachusetts Gaming Commission will be subject to rigorous oversight and enforcement by our Investigations and Enforcement Bureau."

According to records of the Pennsylvania Gaming Control Board's July 17 meeting, the gambler, who had been banned for life from the casino after his first exclusion violation, did not draw the attention of casino operators during his extended time on the floor, despite his photograph having been posted in the back office as a repeat offender.

He was detected after approximately 70 hours around the craps tables when a surveillance camera zoomed in on the iPad he was holding and staff saw his name on it.

Rosemarie Cook, vice president of gaming at SugarHouse, told Pennsylvania regulators, "I assure you it was not a case of being asleep at the wheel."

She said the gambler did not stick out in any way or raise red flags with unruly behavior, unkempt appearance or high wagering. He spent three-quarters of his time at the casino off the tables, playing 38 times in sessions lasting from two to 12 minutes. And he was at the tables only once during a shift change, when a table supervisor would normally point out any extended playing to the next shift supervisor.

"He was just average, and he looked average," Ms. Cook said.

"It boggles my mind that somebody can be in your facility for three days in one instance, four days in another, a known compulsive gambler on the list and not be recognized," Pennsylvania Gaming Board Commissioner Gregory C. Fajt told SugarHouse officials. "It's disheartening to me. We spend a lot of time and effort in our compulsive gambling program."

Pennsylvania regulators noted that some casinos in that state use costly facial-recognition software to detect people who are on the exclusion list.

SugarHouse maintains a binder with print photos sent by the state of the roughly 5,000 people on the list.

Ms. Cook said the state would need to provide digital versions, rather than print copies, of the images to effectively use facial-recognition systems.

The Pennsylvania board rejected without comment a proposed negotiated settlement agreement at its July meeting.

Gaming Control Board spokesman Doug Harbach said another proposed settlement was not on the draft agenda for the board's Aug. 21 meeting. The earliest it would most likely be re-addressed would be Sept. 18.

Jon Scolnik, a national representative of Unite Here casino workers union, which has paid for a mailing to Millbury residents critical of Rush Street Gaming, asked in an interview, "What's Rush Street Gaming's plan for Millbury? Are they planning to install software?"

The Millbury Planning Board will continue its special permit hearing Aug. 26 for the proposed slots parlor on McCracken Road near Route 146.

A townwide referendum on a host community agreement with Mass Gaming & Entertainment will be held Sept. 24.

If the proposal receives town approval, developers must file a phase 2 license application by Oct. 4. The Gaming Commission will award the sole statewide slots license around the end of the year.